Method and device for manufacturing electric resistance bodies



CE FOR MANUFACTURING ELECTRIC RESISTANCE BODIES 2 Sheets-Sheet l HE'NDRIKJAN VAN DEN BERGE INVENTORS BY AGENT C. DE LANGE ET AL METHOD AND DEVI CCFBEUS DE LANGE! PETER GOEIDB AND March 14, 1950 Filed Nov. 2'7, 1946 March 14, 1950 c. DE LANGE ETAL 2,500,605

- METHOD AND DEVICE FOR umumc'ruamc ELECTRIC RESISTANCE BODIES 2 Sheets-Sheet 2 Filed NOV. 27, 1946 CORNELIS DE LAME; PIB'TER 0020a AND HEINDRIK JAN VAN DEN SERGE! eww/ AGENT Patented Mar. 14, 1950 METHOD AN D DEVICE FOR MANUFACTUR ING ELECTRIC RESISTANCE BODIES Cornelis de Lange, Pieter Goede, and Hendrik Jan van den Berge, Eindhoven, Netherlands, as= signors to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application November 27, 1946, Serial No. 712,556 In the Netherlands August 4, 1945 Section 1, Public Law 690, August s, 1946 Patent expires August 4, 1965 Numerous electricresistances are constituted by elongated resistance bodies which may be commanded by a tap. As a rule, the resistance body is constituted by an insulating carrier having applied to it a thin layer of resistance material, for example a layer of wire turns, a metallic layer applied by vaporisation, or a layer consisting of a conductive powder, such as graphite, and an insulating binder, for example a synthetic resin. However, it is also possible for the body to consist wholly of resistance material.

In such resistances the resistance value between one of the extremities of the resistance body and the movable tap is a function of the position of the tap. This function may be of different kinds. Resistances having a linear or a logarith mic variation are frequently used in practice and are obtained by varying the dimensions and/or the specific resistance of the resistance material as a function of the distance to one extremity of the resistance body. The accuracy of such resistances is, as a rule, not so great as to permit the provision, in addition to the tap, of a graduation and to permit their use in measuring devices instead of the tapping or decade resistances commonly employed in the latter.

The present invention relates to a method and to a device for manufacturing elongated resistance bodies which satisfy very high requirements of accuracy, especially so far as it is essential to fulfill a definite function for the value of the resistance between one extremity and a variable point of the resistance on the one hand and the distance to that extremity on the other hand.

According to the invention, the manufacture of the resistance body begins at one extremity and continues in the longitudinal direction of the body,.the value of the resistance of the part that is completed being continuously compared to that part of a standard resistance which is located between a fixed point and a tap which moves along this resistance at a speed proportional to that at which the resistance body is manufactured.

The resistance body may be formed in different manners which are inter alia known per se. it

8 Claims. (Cl. 51281) fully with reference to a few practical examples shown in' the accompanying drawings.

may be formed either by winding a wire onto an insulating carrier, or by coating such a carrier with conductive material, for example with a metallic layer applied by vaporisation. However, it may also be formed by removing resistance material from the body, for example by grinding off.

This method and the device by which it may be carried out, together with several forms of construction, preferably used, will be described more position.

Figure 1 illustrates diagrammatically the principle of a device according to the invention.

Figure 2 shows a resistance body manufactured by the process according to the invention, which is particularly suited to be incorporated in a potentiometer having arotary contact.

Figure 3 shows in greater detail, but also diagrammatically, a device according to the invention for the manufacture of wire resistances.

The device shown in Figure 1 is constituted by a mechanical and an electric portion. The mechanical portion permits of manufacturing a resistance body in such a manner that a definite variation may be given to the relation of the resistance between one extremity and a definite point of the resistance to the distance between 'this extremity and this point. The practical example shown is constituted by a resistance built up from a carrier l and a layer of conductive material 2. This resistance can rotate along a rotary grindstone 3 which is movable in the axial direction of the resistance and in addition in a. direction normal thereto, as indicated by arrows. It is thus possible to remove a more or less thick layer of resistance material from the resistance.

The electrical portion of the device is constituted by an arrangement enabling two resistance values to be compared with each other, for example by a Wheatstone bridge. One of the resistances to be compared is constituted by the completed portion 4 of the resistance to be manufactured. It is located between a tap 5, which slides on a terminal contact 6 of the resistance, and a tap I which is provided at the same distance therefrom as the grinding device 3. The second resistance is constituted by that portion 8 of a standard resistance 9 which is located between the corner ill of the bridge connection and a. movable tap ii. The bridge is completed by two resistances l2 and I3, a galvanometer H, and a source of supply IS. The taps l and H, together with the grinding device 3, are mechanically coupled so as to be jointly movable.

In manufacturing a resistance the grinding device is initially placed on the extreme left. The two resistances to be compared have the value zero. The values of the resistances increase as the grinding device is displaced to the right. As

long as the desired ratio between the portion I of the standard resistance 9 and the completed portion 4 of the resistance to be manufactured is retained, the galvanometer It occupies its zero When the completed portion has too low a resistance, the galvanometer shows a deflection in a definite direction and it will be necessary to remove a larger amount of material by bringing the grinding device more closely to the resistance.

It is similarly possible to manufacture a resistance body particularly suited to be incorporated in a potentiometer having a rotary sliding contact. Such a resistance body is shown in Figure 2; it is constituted by an insulated carrier and a conductive layer 2, which may consist of a conductive powder, for example graphite, and an insulating binder, for example synthetic resin. The resistance body is shown in its initial form. In potentiometers of this kind it is frequently desirable that the ratio between the resistance value and the angular displacement of the tap should exhibit a definite characteristic. The use of the method according to the invention permits of this requirement to be readily fulfilled if parts of the resistance body, for example those according to the dotted line l6, are ground off. It is evident that the resistance body must not be ground off to such extent that the width which remains for the formation of a layer I1 is insufficient. The method according to the invention has the further advantage that differences in the specific resistance of the resistance material, in the present instance of a conductive layer, are neutralized of their own accord.

The second practical example that will be described is a device for the winding of wire resistances,

The resistance to be manufactured is constituted by an insulated carrier (see Fig. 3) on which a resistance wire Hi from a supply reel |8a may be wound. The insulating carrier which may have, for example, the shape of a flat band is mounted to this end in a rotary holder l9, whilst one of its extremities is held in position by a clamp 20 which follows the rotary motion. Clamp 20 is placed on a slide 2| which is coupled' to a piston 22 and a piston rod 23 which can move in a cylinder 24 when a medium, for example oil, is supplied by the pump 25 at one end of the piston or at the other. The oil output of the pump 25 may be regulated by displacement of a lever 26. The pump is driven by a shaft 21, the same shaft which also drives the holder l9.

The slide 2| drives, via gear wheels 28 and 29, a toothed rack 30 in such manner as to displace the latter to an extent which is a multiple of the displacement of the slide. This toothed rack carries a tap II which has the same function as that bearing the same reference numeral, of the device shown in Figure 1.

In this device the length of the standard resistance and the speed at which the tap H is displaced along this resistance are a multiple of the length of the resistance to be manufactured and of the speed at which the resistance is manufactured. For the standard resistance use is preferably made of a wire resistance, the number of turns of which is a multiple of that of the resistance to be manufactured. These steps afford a greater possibility of obtaining a very high accuracy of the standard resistance.

The toothed rack 30 drives, in addition, a cam disc 3| via gear wheels 32, 33, 34 and a chain 35. The assembly constituted by the gear Wheels 33 and 34 and the chain 35 may be displaced in such manner that the gear wheel 33 meshes with the gear wheel 34 or not. The cam disc 3| may displace a. rod 36 by means of the cam with the result that the lever 26 is displaced. This displacement may be influenced in addition by hand by means of a lever 31 and an eccentric 38.

The direction of flow of the medium may be reversed with the aid of a cock 39.

The electrical portion of the device, which may be identical with that of the device of Figure 1, is not shown. The completed portion of the resistance to be manufactured is measured between the clamp 20 and the tap 5, which has the shape of a pair of rollers. The comparison resistance 3 is located, as before, between the corner ID of the bridge circuit and the tap The device may be driven by a motor 40 via an electrically operated coupling 4|.

The cam disc 3| has such a shape as to regulate the oil supply in such manner that the resistance 4 acquires as much as possible the desired value. Small differences are, however, always liable to 'occur, for example due to irregularities in the material or in the thickness of the wire. They cause a deflection of the galvanometer It, thus giving an indication in what direction the differences may be corrected by hand with the aid of the lever 31.

In this device the winding speed is constant whereas the displacement of the carrier is adjustable; the reverse is, however, also possible.

When the resistance is wholly completed, it may be bent into a circular shape and used in a potentiometer having a rotary sliding contact.

In this executional example the band-shaped carrier has the same width throughout. If essential differences in the resistance per cm length must be obtained, the winding pitch between the different parts exhibits great differences. Should this cause difficulty, use may be made of a band of variable width.

What we claim is:

1. A method of manufacturing precision electrical resistors having a precisely defined resist ance characteristic which comprises the steps of continuously forming an electrical resistance element on a support, continuously comparing the resistance value of the formed portion of the resistor with a corresponding portion of a standard resistance having a desired calibration, and continuously controlling the resistance of said formed portion to follow the calibration of said standard resistance element.

2. A method of manufacturing precision electrical resistors having a precisely defined resistance characteristic which comprises the steps of continuously winding electrical resistance wire on a support, continuously comparing the resistance value of the wound portion of the resistor with a corresponding portion of a standard resistance having a desired calibration, and continuously adjusting the rate of winding the electrical resistance wire to follow the calibration of said standard resistance element.

3. A method of manufacturing precision electrical resistors having a precisely defined resistance characteristic which comprises th steps of continuously coating an insulating supporting base with a conductive material, continuously comparing the resistance value of the coated portion of the base with a corresponding portion of a standard resistance having a desired calibration, and continuously controlling the rate of coating the base to follow the calibration of said standard resistance element.

4. A method of manufacturing an electrical resistor as claimed in claim 3 wherein a metal layer is applied by vaporisation.

5. A method of manufacturing an electrical 5 x resistor having a precisely defined resistance characteristic which comprises the stepsof continuously removing alayer of resistance material from a base coated with said material, continuously comparing the resistance value of the removed portion with a corresponding portion of a standard resistance having a desired calibration, and continuously controlling the resistelement having a desired calibration, means to continuously connect a portion of said standard resistance element having a resistance value corresponding to the resistance being formed as a balancing arm of said bridge arrangement; a

. movable contact on said standard resistance element, a movable contact on said resistor, and means responsive to said null indicating bridge arrangements for controlling the formation of said resistance element being formed whenever said null indicating bridge is unbalanced.

8. A device for manufacturing precision electrical resistors which comprises a mandrel for winding a wire wound resistance element, a null indicating bridge arrangement, means to connect the resistance element as one arm of the bridge, a standard wire wound resistance element hav- Number ing a desired calibration, means to connect a portion of said standard resistance element having a resistance value corresponding to the wound portion of the resistance element being wound on the mandrel as a balancing arm of said bridge arrangement, a continuously movable contact on said resistor, a movable contact on said standard resistance element, means coupling said resistor contact and said standard resistance contact whereby said resistor contact follows said standard resistance contact and the resistance of said resistor can be calibrated to follow the calibration of the standard resistance, means to continuously rotate said mandrel to wind a resistance element, and means responsive to deviations from a null indication on said bridge for controlling the speed of winding said resistance element to thereby obtain a resistance element having a calibration comparabl to the calibration of the standard resistance.

CORNELIS n: LANGE.

PIEI'ER GOEDE.

HENDRIX JAN van mm BERGE.

REFERENCES crmn The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Stone May 3, 1927 Jones July 12, 1927 Stroughton Aug. 9, 1927 Flanzer et al June 12, 1934 Richter May 23, 1939 Leathers et a1. May 18, 1943 Gaiser Sept. 5, 1944 

